CN106430244A - Method for recovering and purifying ammonia gas from ammonia nitrogen wastewater - Google Patents

Abstract

The invention discloses a method for recovering and purifying ammonia gas from ammonia nitrogen wastewater, belonging to the field of wastewater treatment technology and resource utilization. The present invention comprises the following steps: 1. The waste water containing ammonia nitrogen is blown off under alkaline conditions by means of air blow-off to remove most of the ammonia nitrogen and volatile organic matter in the waste water. (Crude ammonia gas) for follow-up treatment; 2. The crude ammonia gas is cooled by heat exchange to separate the water vapor in the crude ammonia gas; 3. The crude ammonia gas is adsorbed and purified through the adsorption process to remove most of the inclusions in the crude ammonia gas Volatile organic matter; 4. Use water or sulfuric acid to absorb the ammonia gas after adsorption and purification; 5. Regenerate the saturated adsorption material to realize recycling. The invention greatly improves the stripping efficiency of ammonia nitrogen on the premise of saving energy consumption, and the ammonia gas can be recycled and effectively purified, thereby ensuring the recoverable value of recovered resources.

Description

A method for recovering and purifying ammonia from ammonia nitrogen wastewater

technical field

The invention belongs to the field of waste water treatment technology and resource utilization, and more specifically relates to a method for recovering and purifying ammonia from ammonia nitrogen waste water.

Background technique

High-concentration ammonia-nitrogen wastewater comes from a wide range of sources, including residual ammonia water from coking plants, coal gasification wastewater, monosodium glutamate wastewater, and landfill wastewater. The ammonia nitrogen concentration of the above various wastewaters is different, and the composition is relatively complex, containing more organic matter. Excessive ammonia nitrogen content in the water body will cause the deterioration of the ecological environment of the water body, endanger aquatic organisms and human health, cause eutrophication of the water body, and increase the cost of water treatment.

At present, for the treatment technology of high ammonia nitrogen wastewater, ammonia nitrogen needs to be separated from the water first, and then the sewage enters the subsequent biochemical unit for biological denitrification. At present, the common ammonia nitrogen separation processes in China include ammonia distillation method and stripping method. The domestic ammonia distillation process is mainly a direct ammonia distillation process, using water vapor as a heating agent, so that the equilibrium vapor pressure of ammonia on the circulating water surface is greater than the partial pressure of ammonia in the heat carrier, and the gas-liquid two-phase mass transfer and heat transfer make the Ammonia gas is gradually released from the circulating water. Ammonia nitrogen is recovered to make ammonia water, which is directly reused in the ammonium sulfate process or reacted with flue gas to make ammonium sulfate. The direct ammonia distillation process consumes a lot of energy, it is difficult to completely release the ammonia nitrogen in the wastewater, and the ammonia nitrogen recovery rate is low; the ammonia distillation temperature is high (105-110°C), and some volatile organic compounds volatilize together with the ammonia gas during the ammonia distillation process out, affecting the purity quality of recovered ammonia.

The ammonia nitrogen stripping method is one of the main methods for ammonia nitrogen separation in wastewater. The ammonia gas stripped out is mainly absorbed by water or sulfuric acid to make ammonia water or ammonium sulfate solution, but the main problems of this method are: 1. High reaction temperature, The heat energy consumption is large, and the ammonia nitrogen in the wastewater is difficult to be completely released, and the ammonia nitrogen recovery rate is low; 2. The gas-water ratio is large in the stripping process, and the power consumption is large; 3. During the stripping process, some low-boiling point, volatile The organic matter overflows with the ammonia gas, resulting in the recovery of ammonia water or ammonium sulfate with low purity and containing more organic impurities.

The existing Chinese patent application publication number is CN 102060406 A, and the patent application document with the application publication date of May 18, 2011 discloses an integrated process for closed-circuit treatment of ammonia-nitrogen wastewater with high-efficiency stripping and tail gas ammonia resource utilization. It is CN 103318918 A, and the patent application document with the publication date of application on September 25, 2013 discloses a method for purifying and recovering ammonia. Both of the above two patents propose a process technology for efficient stripping and absorption of ammonia nitrogen, which improves the ammonia nitrogen High stripping efficiency, reducing energy consumption in the traditional ammonia distillation and stripping process, but no ideal solution has been proposed for the problem of low purity ammonia recovery and many organic impurities. The Chinese patent application publication number is CN 102030438 A, and the patent application document published on April 27, 2011 discloses a treatment method for ammonia nitrogen wastewater. The stripping method has the disadvantage of low treatment efficiency for low-concentration ammonia-nitrogen wastewater, but the use of resin to adsorb ammonia nitrogen does not consider the possible cooling of water vapor in the gas in the resin. The cooled water vapor will cause a rapid increase in resin pressure drop and increase ammonia nitrogen. The dissolution in the resin unit not only consumes a large amount of power energy, but also is not conducive to the recovery efficiency of ammonia nitrogen, and the cost is high.

The Chinese patent application number is 201410078586.3, and the patent application document published on September 9, 2015 discloses a treatment equipment for wastewater containing ammonia nitrogen, including a stripping tower, a heater, a catalyst reactor and a gas-to-gas heat switch. Ammonia-nitrogen-containing wastewater and stripping gas are stripped in a stripping tower to become stripped wastewater and ammonia-containing gas. The heater heats the ammonia-containing gas, and the ammonia-containing gas is treated by the catalyst reactor to oxidize the ammonia in the gas to obtain a treated gas. The gas-to-gas heat exchanger is used for exchanging heat between the ammonia-containing gas and the treated gas. Wherein, the heat exchange efficiency of the gas-to-air heat exchanger is adjusted accordingly according to the total calorific value of the ammonia-containing gas, so that the heat exchange efficiency is correspondingly adjusted down as the total calorific value increases, or Let the heat exchange efficiency increase correspondingly with the decrease of the total calorific value. However, this patent is only a treatment method for ammonia-nitrogen-containing wastewater, not a process of refining ammonia water. It also clearly states in claim 6 that "the ammonia-nitrogen-containing wastewater contains volatile organic compounds, and at least part of the volatile organic compounds is It is taken out by gas lift"; the Chinese patent application publication number is CN 102730718 A, and the application publication date is that the patent application document on October 17, 2012 discloses an ammonia refining system and a refining method for ammonia. The refinement (purification) of crude ammonia is carried out by gasification, adsorption of impurities, condensation and separation of ammonia. This method uses synthetic zeolite to adsorb moisture and low-volatility impurities in crude ammonia gas, but does not consider the influence of higher temperature gas on the adsorption performance of the adsorbent. Generally, the higher the gas temperature, the less the adsorbent has on the volatile organic compounds. The lower the capture efficiency, and the moisture contained in the crude ammonia gas will easily saturate the adsorption material, reduce the adsorption capacity, and thus increase energy consumption and cost.

Contents of the invention

1. The problem to be solved

Aiming at technical problems such as the high energy consumption of the ammonia nitrogen stripping process of the existing ammonia nitrogen wastewater, the influence of high temperature on the adsorption material and the influence of water vapor on the adsorption process in the crude ammonia adsorption and purification process, and the low purity of the recovered product (ammonia water or ammonium sulfate), etc., The invention provides a method for recovering and purifying ammonia gas from ammonia-nitrogen wastewater, which uses gas heat exchange and condensation as a characteristic process, and uses condensed water as an absorption liquid for recycling, thereby realizing enhanced removal, efficient recovery and purification of ammonia nitrogen.

2. Technical solution

In order to solve the above problems, the technical scheme adopted in the present invention is as follows:

A method for recovering and purifying ammonia from high-ammonia-nitrogen wastewater, comprising the steps of:

1) The ammonia-nitrogen-containing wastewater is stripped under alkaline conditions through the air stripping process, and a quantitative denitrification agent is added during the stripping process, and the reaction temperature and gas-water ratio are controlled; the liquid phase derived from the air stripping process Part of the ammonia nitrogen concentration reaches the biochemical treatment standard and goes to the sewage treatment station for treatment, and the gas phase part (crude ammonia gas) is processed in step 2);

2) The gas phase part (crude ammonia gas) derived from the step 1) air stripping process is subjected to heat exchange, and the gas is cooled, and the water vapor in the crude ammonia gas is first condensed and separated to reduce the interference of water vapor to subsequent steps, and the condensate is used Make ammonia absorbing liquid and recycle, and gas enters step 3) processing;

3) Adsorption and purification of the crude ammonia after cooling, through this step, most of the volatile organic impurities mixed in the crude ammonia can be removed;

4) Using water or sulfuric acid as the absorbing liquid to absorb the ammonia gas after adsorption and purification in step 3) to produce ammonia water or ammonium sulfate, which can be recycled as products.

Furthermore, in this process, the gas heat exchange is moved forward between the stripping and adsorption processes, which not only ensures that the interference of the water vapor blown out on the adsorption process is eliminated, but also enhances the absorption efficiency of arginine.

Furthermore, the condensate collected in the pre-gas cooling step contains a large amount of ammonia, and this part of the condensate is used as the absorption liquid in the refined ammonia absorption step, which not only realizes the recycling of the condensate, but also improves the overall Ammonia recovery efficiency.

Further, in the step 1), the wastewater pH is adjusted to 9-14, the wastewater temperature is controlled at 20°C-90°C, the stripping time is 0.5-10h, and the gas-water ratio is (300-5500):1, After the wastewater is blown off with ammonia gas, the residual sewage enters the biochemical unit for subsequent treatment.

Further, the dosage of the denitrification agent in the step 1) is 0-30ppm, the so-called denitrification agent consists of ethylene glycol deaminase 10-20%, ferrate 5-10%, organic carboxyl 5-30% of acids, 5-30% of hydrogen peroxide are miscible in the aqueous solution (mass fraction), and can also be other ammonia nitrogen removal products with similar functions.

Furthermore, in the step 2), after the crude ammonia is cooled by heat exchange, the condensed moisture is removed through gas-liquid separation. The heat exchange process can be tap water heat exchange or air heat exchange. The gas-liquid separation mainly adopts Gas-liquid gravity is different to achieve.

Further, in the described step 3), the adsorption filler is mainly one or more combinations of porous materials such as activated carbon, zeolite, ceramsite, molecular sieve, natural adsorbent, chitosan, resin, etc., can be Most of the organic impurities in the crude ammonia gas are retained to realize the purification of ammonia gas. After the adsorption filler is saturated, it can be desorbed and regenerated with steam. After the adsorption filler is regenerated, it can be recycled, reducing the economic cost of the ammonia recovery and refining system.

Furthermore, in the step 4), the absorption liquid used for absorbing the adsorbed and purified ammonia gas can be water or sulfuric acid, the concentration of sulfuric acid can be 1%-98%, and the ammonia nitrogen absorption efficiency is as high as 99%.

Further, the present invention can reasonably balance energy, fully realize resource reuse, and simultaneously solve the problems of denitrification of ammonia nitrogen wastewater and recovery and purification of ammonia water.

The existing ammonia nitrogen wastewater treatment process has the following technical problems: (1) The current ammonia nitrogen stripping method treats high ammonia nitrogen wastewater, and the denitrification efficiency is not high enough, resulting in high pressure for subsequent wastewater biochemical denitrification, and the recovery of ammonia water or ammonium sulfate is not pure enough. Direct use, often for solid waste disposal, high treatment cost; (2) The current ammonia water refining technology does not consider energy balance from the system, and does not analyze and take targeted measures for the types of ammonia nitrogen stripping and possible coexisting impurities in ammonia nitrogen wastewater Measures: Commonly used purification and adsorption methods are used in ammonia gas obtained by blowing off ammonia nitrogen wastewater, and there are generally technical problems such as low adsorption efficiency, frequent regeneration, insufficient adsorption of organic impurities, and difficulty in reaching recycling standards for products. Therefore, these technologies The method is not applicable to the ammonia nitrogen recovery and purification field of ammonia nitrogen wastewater treatment, and cannot solve the technical problems in this field; (3) the technology of the present invention fully analyzes the typical characteristics of the ammonia nitrogen wastewater ammonia nitrogen recovery and purification field, on the basis of traditional technology, Creatively combine key points such as catalytic stripping, pre-gas heat exchange, condensate circulation absorption, and impurity adsorption to achieve significant beneficial effects and solve high-ammonia-nitrogen waste water efficient treatment and resource recycling. Common in the industry It is difficult for technicians to realize the beneficial effects of the patented method through simple combination or adjustment of the process route; (4) The technical creation of this patent arranges and combines the process units, changes the traditional conventional thinking, and makes the method more suitable for technical problems in this field Effective solution, and the key parameters of the process mentioned in the patented technology need to be obtained through a series of experiments, which is of great significance to solve the technical problems in this field. (5) The method provides a method for reclaiming and purifying ammonia from ammonia-nitrogen waste water, and solves the following problems: 1) the problem of large energy consumption in the ammonia-nitrogen stripping process; 3) the problem that the purity of the recovered product (ammonia or ammonium sulfate) is not high.

A method for recovering and purifying ammonia from ammonia-nitrogen wastewater in the present invention is an innovative research aimed at technical problems such as the current ammonia-nitrogen wastewater ammonia-nitrogen stripping efficiency is not high enough, the purity of ammonia refining is not enough, and the existing refining system needs to be improved. On the basis of the existing technology, the invention technology uses gas heat exchange and condensation as the characteristic process, and uses the condensed water as the absorption liquid for recycling, so as to realize the enhanced removal, efficient recovery and purification of ammonia nitrogen. At present, although there are many technologies in the industry to solve the treatment of ammonia nitrogen wastewater, the main idea is to blow off the ammonia nitrogen in the wastewater and reduce the difficulty of wastewater denitrification treatment. However, the current treatment technologies generally have insufficient stripping efficiency, resulting in The subsequent biological denitrification of sewage is still under great pressure. In addition, when the ammonia gas obtained by stripping is absorbed and reused, the purity of ammonia water or ammonium sulfate is generally insufficient, and it is difficult to directly reuse it. It is often treated as solid waste directly, which not only fails to realize resource reuse. , and treating it as solid waste increases the cost of ammonia nitrogen wastewater treatment; on the other hand, although there are many patented technical methods for refining or purifying ammonia water, these patented technical methods are still too simple and extensive, and many detailed problems have not been properly resolved. In the actual use process, there are shortcomings such as insufficient ammonia nitrogen stripping efficiency, insufficient purity of refined ammonia, low energy utilization efficiency, and high economic cost; the technology of the present invention starts from the perspective of efficient denitrification treatment of ammonia nitrogen wastewater and resources, refining and reuse. Consider the technical method from the perspective of the overall system process, and creatively combine the key points such as catalytic stripping, gas heat exchange front, condensate circulation absorption, impurity adsorption, etc., synergistic effect, achieve significant beneficial effects, and solve the problem of efficient treatment of high ammonia nitrogen wastewater and resource reuse.

3. Beneficial effect

Compared with the prior art, the beneficial effects of the present invention are:

(1) The present invention adopts low-temperature blowing of air, which reduces the amount of steam used, can realize energy saving and consumption reduction, and simultaneously reduces the amount of waste water increased by steam condensation, and reduces the treatment scale and operating costs of subsequent sewage treatment units;

(2) The present invention adopts air low-temperature blow-off, and by adding a denitrification agent, the reaction temperature can be reduced, the denitrification efficiency can be improved, the volatilization of high-boiling organic matter can be reduced, and the processing load of the adsorption material can be effectively reduced. It can effectively remove most of the organic matter mixed in the crude ammonia gas, and improve the recovery value of ammonia gas;

(3) The present invention puts the gas cooling process in front, which is beneficial to reduce the influence of high-temperature gas on the performance of the adsorption material, and eliminates the influence of water vapor on the adsorption process by separating water through gas cooling, reduces the power consumption of the adsorption process, and realizes energy efficiency. reasonable balance;

(4) The present invention adopts adsorption purification, which can realize the enrichment of organic pollutants, and properly handles the desorbent, which can reduce the load of wastewater treatment; the adsorption filler can be desorbed and regenerated after being adsorbed and saturated, without secondary pollution;

(5) The method of the present invention has a wide application range, and can realize the efficient treatment of waste water with an ammonia nitrogen content of 1% to 20%;

(6) The ammonia nitrogen wastewater treatment method adopted in the present invention carries out ammonia nitrogen recovery to high ammonia nitrogen wastewater, the ammonia nitrogen recovery rate is more than 99%, and the ammonia nitrogen purity of recovery is higher than 96%;

(7) The ammonia-nitrogen wastewater treatment method adopted in the present invention processes the ammonia-nitrogen-containing wastewater through proper pretreatment, the system ammonia-nitrogen removal rate is more than 95%, and the ammonia-nitrogen content of the treated wastewater is less than 100mg/L, which reduces the load of subsequent wastewater treatment At the same time, the concentration of ammonia nitrogen in the effluent can be controlled by adjusting the parameters of the stripping process, so that it can more flexibly adapt to the nitrogen demand of the subsequent biochemical unit.

Description of drawings

Fig. 1 is the efficient treatment process flowchart of the present invention;

Fig. 2 is the treatment effect figure in the embodiment of the present invention 3: illustrated 1) denitrification agent is conducive to the raising of blow-off efficiency; 2) as time goes on, the blow-off efficiency of ammonia is up to more than 95%;

detailed description

The present invention will be further described below in conjunction with specific embodiments.

Example 1

Using the method provided by the invention to carry out a small test on the actual residual ammonia water in a coking plant in Shanxi, the influent COD and NH ₃ -N are about 5200mg/L and 1900mg/L respectively.

The remaining ammonia water is firstly removed by conventional pretreatment methods to remove oil, suspended solids, etc. in the water, and the pretreated residual ammonia water enters the air stripping system, and 5ppm of denitrification agent is added. The denitrification agent is composed of 10% ethylene glycol deaminase , 5% ferrate, 5% organic carboxylic acids, 5% hydrogen peroxide are miscible in aqueous solution. And 30% NaOH solution was used to control the pH of the wastewater during the reaction process to be 11, the reaction temperature was controlled to be 30°C, the experimental gas-water ratio was 800:1, and the stripping time was 2h. After the crude ammonia gas exported from the air stripping system is cooled by the heat exchanger, the cooled liquid undergoes gas-liquid separation and returns to the stripping tower for secondary stripping. The cooled ammonia gas enters the adsorption device for the adsorption of organic waste , the adsorbent used in the experiment is activated carbon. The gas after adsorption and purification enters the gas absorption device, and the experiment uses 3.5% sulfuric acid as the absorption liquid to absorb ammonia gas.

After 2 hours of air stripping, the NH ₃ -N of the remaining ammonia water dropped from 1900mg/L to 53mg/L, and the stripping efficiency was as high as 97.2%. The adsorption capacity of activated carbon for gaseous organic matter. The COD of the raw water is 4500mg/L, the COD of the absorption liquid is 89mg/L, and the purity of the ammonium sulfate is 96.34%, which can be recovered as a product.

Example 2

Using the method provided by the invention to test the actual remaining ammonia water in a coking plant in Shanxi, the influent COD and NH ₃ -N are about 5200mg/L and 1900mg/L respectively.

The remaining ammonia water is firstly removed by conventional pretreatment methods to remove oil, suspended solids, etc. in the water, and the pretreated residual ammonia water enters the air stripping system without adding denitrification agent, and uses 30% NaOH solution to control the pH of the wastewater during the reaction process. 14. Control the reaction temperature to 90°C, and the experimental gas-water ratio to 5500:1. After the crude ammonia gas exported from the air stripping system is cooled by the heat exchanger, the cooled liquid undergoes gas-liquid separation and returns to the stripping tower for secondary stripping. The cooled ammonia gas enters the adsorption device for the adsorption of organic waste , the adsorbent used in the experiment is activated carbon. The gas after adsorption and purification enters the gas absorption device, and the experiment uses 98% sulfuric acid as the absorption liquid to absorb ammonia gas.

After 10 hours of air stripping, the NH ₃ -N of the remaining ammonia water dropped from 1900mg/L to 65mg/L, and the stripping efficiency was as high as 96.6%. The adsorption capacity of activated carbon for gaseous organic matter. The COD of the raw water is 4500mg/L, the COD of the absorption liquid is 152mg/L, and the ammonium sulfate can be recovered as a product.

Example 3

Using the method provided by the invention to test the actual remaining ammonia water in a coking plant in Shanxi, the influent COD and NH ₃ -N are about 5200mg/L and 1900mg/L respectively.

The remaining ammonia water is firstly removed by conventional pretreatment methods to remove oil, suspended solids, etc. in the water, and the pretreated residual ammonia water enters the air stripping system, and 15ppm of denitrification agent is added. The denitrification agent is composed of 15% ethylene glycol deaminase , ferrate 7%, organic carboxylic acids 15%, hydrogen peroxide 15% miscible in aqueous solution, and use 30% NaOH solution to control the pH of the wastewater in the reaction process to be 9, control the reaction temperature to 70 °C, and the experimental gas The water ratio is 3000:1. After the crude ammonia gas exported from the air stripping system is cooled by the heat exchanger, the cooled liquid undergoes gas-liquid separation and returns to the stripping tower for secondary stripping. The cooled ammonia gas enters the adsorption device for the adsorption of organic waste , the adsorbent used in the experiment is activated carbon. The gas after adsorption and purification enters the gas absorption device, and the experiment uses 98% sulfuric acid as the absorption liquid to absorb ammonia gas.

After 5 hours of air stripping, the NH ₃ -N of the remaining ammonia water dropped from 1900mg/L to 73mg/L, and the stripping efficiency was as high as 95%. The adsorption capacity of activated carbon to gaseous organic matter is improved. The COD of the raw water is 4500mg/L, the COD of the absorption liquid is 161mg/L, and the ammonium sulfate can be recovered as a product.

Example 4

Using the method provided by the invention to test the actual remaining ammonia water in a coking plant in Shanxi, the influent COD and NH ₃ -N are about 5200mg/L and 1900mg/L respectively.

The remaining ammonia water is firstly removed by conventional pretreatment methods to remove oil, suspended solids, etc. in the water, and the pretreated residual ammonia water enters the air stripping system, and 30ppm of denitrification agent is added. The denitrification agent is composed of 20% ethylene glycol deaminase , ferrate 10%, organic carboxylic acids 30%, hydrogen peroxide 30% miscible in aqueous solution, and use 30% NaOH solution to control the pH of the wastewater in the reaction process to be 12, control the reaction temperature to 20 ℃, and the experimental gas The water ratio is 300:1. After the crude ammonia gas exported from the air stripping system is cooled by the heat exchanger, the cooled liquid undergoes gas-liquid separation and returns to the stripping tower for secondary stripping. The cooled ammonia gas enters the adsorption device for the adsorption of organic waste , the adsorbent used in the experiment is activated carbon. The gas after adsorption and purification enters the gas absorption device, and the experiment uses 98% sulfuric acid as the absorption liquid to absorb ammonia gas.

After 0.5h of air stripping, the NH ₃ -N of the remaining ammonia water dropped from 1900mg/L to 173mg/L, and the stripping efficiency was as high as 90%. , to increase the adsorption capacity of activated carbon on gaseous organic matter. Raw water COD is 4500mg/L. The COD in the absorption liquid is 41mg/L, and ammonium sulfate can be recovered as a product.

Example 5

Using the method provided by the invention to carry out a small test on the actual waste water of a certain coal gas plant in Henan, the influent COD and NH ₃ -N are about 24300mg/L and 78000mg/L respectively.

The wastewater is firstly treated with conventional pretreatment methods to remove oil, suspended solids, etc. in the water, and the pretreated wastewater enters the air stripping system, and 30ppm of denitrification agent is added. The denitrification agent consists of ethylene glycol deaminase 10%, high iron 5% acid salt, 15% organic carboxylic acid, 30% hydrogen peroxide are miscible in aqueous solution, and 30% NaOH solution is used to control the pH of waste water during the reaction process to be 12-13, and the reaction temperature is controlled to be 60°C. After 5 hours of air stripping, the NH ₃ -N of the remaining ammonia dropped from 78000mg/L to 200mg/L, and the COD dropped from 24300mg/L to 4300mg/L. The experimental air-water ratio is 1500:1.

The gas exported from the air stripping system is cooled and then enters the adsorption device for adsorption of organic waste. The adsorbent used in the experiment is macroporous resin. The gas after adsorption and purification enters the gas absorption device, and the experiment uses 30% sulfuric acid as the absorption liquid to absorb ammonia gas. The COD in the absorption liquid is 70.8mg/L, and the purity of ammonium sulfate is 99.89%, which can be recovered as a product. The saturated resin is desorbed and regenerated using steam.

Example 6

Using the method provided by the invention to carry out a small test on the actual residual ammonia water in a coking plant in Guangxi, the influent COD and NH ₃ -N are about 8500mg/L and 11000mg/L respectively.

The remaining ammonia water is firstly removed by conventional pretreatment methods to remove oil, suspended solids, etc. in the water, and the pretreated residual ammonia water enters the air stripping system, and 15ppm of denitrification agent is added. The denitrification agent is composed of 20% ethylene glycol deaminase , 10% ferrate, 25% organic carboxylic acids, and 18% hydrogen peroxide are miscible in an aqueous solution, and 30% NaOH solution is used to control the pH of the wastewater in the reaction process to be 9-10, and the reaction temperature is controlled to be 40°C. After 4 hours of air stripping, the NH ₃ -N of the remaining ammonia dropped from 11000mg/L to 80mg/L, and the COD was 7600mg/L. The experimental air-water ratio is 1300:1.

The gas exported from the air stripping system is cooled and then enters the adsorption device for the adsorption of organic waste. The adsorbent used in the experiment is synthetic zeolite. The gas after adsorption and purification enters the gas absorption device, and the experiment uses 7% sulfuric acid as the absorption liquid to absorb ammonia gas. The COD in the absorption liquid is 40mg/L, and the purity of ammonium sulfate is 98.19%, which can be recovered as a product.

Example 7

Using the method provided by the invention to carry out a small test on the actual residual ammonia water in a coking plant in Henan, the influent COD and NH ₃ -N are about 3300mg/L and 4400mg/L respectively.

The remaining ammonia water is firstly removed by conventional pretreatment methods to remove oil, suspended solids, etc. in the water, and the pretreated residual ammonia water enters the air stripping system, and 10ppm of denitrification agent is added, and the denitrification agent is composed of 20% ethylene glycol deaminase , 5% ferrate, 15% organic carboxylic acids, and 15% hydrogen peroxide are miscible in an aqueous solution, and 30% NaOH solution is used to control the pH of the wastewater during the reaction process to be 8-10, and the reaction temperature is controlled to be 40°C. After 2 hours of air stripping, the NH ₃ -N of the remaining ammonia water dropped from 4400mg/L to 70mg/L, and the COD was 2800mg/L. The experimental air-water ratio is 1300:1.

The gas exported from the air stripping system is cooled and then enters the adsorption device for adsorption of organic waste. The adsorption material used in the experiment is macroporous resin. The gas after adsorption and purification enters the gas absorption device, and the experiment uses 20% sulfuric acid as the absorption liquid to absorb ammonia gas. The COD in the absorption liquid is 25mg/L, and the purity of ammonium sulfate is 98.34%, which can be recovered as a product.

Claims (9)

1. a kind of method reclaiming from high ammonia-nitrogen wastewater and purifying ammonia, comprises the steps：

1) in the basic conditions stripping process is carried out to nitrogen-containing wastewater, during stripping, add denitrifier, and control reaction temperature Degree and gas-water ratio；

2) to step 1) in stripping process derive gas phase portion carry out heat exchange, by gas cooling；

3) to step 2) in gas after cooling carry out adsorption and purification and obtain ammonia；

4) adopt absorbing liquid to step 3) in ammonia after purification absorb.

2. a kind of method reclaiming and purifying ammonia from high ammonia-nitrogen wastewater according to claim 1 it is characterised in that：Institute State step 1) in nitrogen-containing wastewater pH be 9～14, temperature control is at 20 DEG C～90 DEG C.

3. a kind of method reclaiming from high ammonia-nitrogen wastewater and purifying ammonia according to claim 1 and 2, its feature exists In：Described step 1) in stripping when a length of 0.5～10h, gas-water ratio be (300～5500):1.

4. a kind of method reclaiming and purifying ammonia from high ammonia-nitrogen wastewater according to claim 1 it is characterised in that：Step The condensate liquid return to step 1 producing in rapid 2)) stripping process in.

5. a kind of method reclaiming and purifying ammonia from high ammonia-nitrogen wastewater according to claim 1 it is characterised in that：Step In rapid 1), the dosage of denitrifier is 0～30ppm.

6. a kind of method reclaiming from high ammonia-nitrogen wastewater and purifying ammonia according to claim 1 or 5, its feature exists In：Described denitrifier is by ethylene glycol deaminase 10～20%, ferrate 5～10%, organic carboxyl acid class 5～30%, dioxygen Water 5～30% is miscible to be formed in aqueous.

7. a kind of method reclaiming and purifying ammonia from high ammonia-nitrogen wastewater according to claim 1 it is characterised in that：Step The adsorption stuffing that in rapid 3), gas is carried out with adsorption and purification is mainly activated carbon, zeolite, haydite, molecular sieve, natural adsorbent, shell One or more of glycan, resin combine.

8. a kind of method reclaiming and purifying ammonia from high ammonia-nitrogen wastewater according to claim 1 it is characterised in that：Step Absorbing liquid in rapid 4) is water or sulfuric acid.

9. a kind of method reclaiming and purifying ammonia from high ammonia-nitrogen wastewater according to claim 8 it is characterised in that：Sulphur The mass concentration of acid is 1～98%.